1. Field of the Invention
This invention relates to strobe apparatus and more particularly to a strobe apparatus which is used for cameras and the like and has variable light distribution characteristics.
2. Related Background Art
As well known, in photographing with a camera, in case the brightness of the object is lower than a certain level, a strobe apparatus will be used. The distribution of the strobe light radiated toward the object from the camera side is usually designed to be of uniform characteristics within the photographed picture angle.
The light distribution characteristics of a conventional strobe apparatus shall be explained in the following with reference to FIGS. 45 to 49. FIG. 45 shows light distribution characteristics in the major side direction of a rectangular photographed picture in a conventionally used strobe apparatus. The abscissa represents angles on the right and left of the optical axis direction of the photographing lens and the ordinate represents flashing amounts from the strobe. The light distribution characteristics in this FIG. 45 correspond to a focal distance of 40 mm of a photographing lens in a camera for photographing a full size of a horizontally long rectangular photographed picture on an ordinary 35 mm wide roll film. As the photographing range in this case is about 25 degrees on one side within the picture angle, the light distribution pattern is set to be 30 degrees on one side with some space. Therefore, the uniform light distribution characteristics will be retained until about 25 degrees on one side within the picture angle.
In case such objects a1, b1 and c1 as are shown in FIG. 46 are photographed with a strobe apparatus having such light distribution characteristics, as shown in FIG. 47, as the distances of the positions of the respective objects a1, b1 and c1 from the position of the camera 1 having the above mentioned strobe apparatus built-in are the same distance l1, a photograph in which the entire photographed picture is substantially properly exposed will be able to be taken.
However, as shown in FIG. 49, in case the positions of the respective objects a2, b2 and c2 are not at the same distance from the strobe built-in camera 1, that is, in case a plurality of objects are at different distances within the picture angle, if such composition as in FIG. 48 is to be photographed, as the nearest object a2 is focused usually in most cases, in FIG. 49, the object a2 of the object distance l1 will be properly exposed but the objects b2 and c2 of the object distances l2 and l3 will be insufficiently exposed.
If the light distribution characteristics optimum to such object states are to be applied to such photographed picture as is shown in FIG. 48, in order to obtain a photograph in which the respective objects a2, b2 and c2 are respectively properly exposed, as shown in FIG. 50, a strobe light having light distribution characteristics corresponding to the respective object distances will have to be radiated.
However, in obtaining such light distribution characteristics as are shown in FIG. 50, there will be a defect that the mechanism of the strobe apparatus will be complicated on a large scale. Therefore, such light distribution characteristics have not yet been realized. In the conventional strobe photographing, only one of a plurality distances within a photographed picture angle has been able to be properly exposed.
Therefore, in case it is necessary to obtain a more natural state, a multi-light flashing with a plurality of strobe apparatus or a bounce light has been used in photographing.
Further, a means wherein a light distribution within a picture angle is varied depending on the type of an object with a one-light strobe apparatus is disclosed in the publications of Japanese utility model application publication No. 28416/1984 and Japanese patent application publication No. 10921/1986. In such means, a liquid crystal or the like which can influence a part of the strobe light permeating range is arranged in front of a flashing part having a uniform light distributing pattern so that, when the shutter is released in the camera, infrared rays will be projected into the picture before the main flash to judge whether an object is located in the near distance or not and, in case the object is located there, the liquid crystal will be driven to reduce the strobe light there so that the light distribution may be varied to prevent the exposure of the object on the near distance side from becoming overexposed.
Now, in the above mentioned conventional means wherein a plurality of strobe apparatus are used or a bounce photographing is made, not only the strobe apparatus will be large and complicated but also the photographer must seek to most suitably set the respective objects and such a highly skilled art will be required that only a limited number of those skilled in the art will be able to use it but it has been difficult for the general users to fully use the conventional means.
Also, in the means disclosed in the above mentioned Japanese utility model application publication No. 28416/1984 wherein the light distribution is made variable by a liquid crystal member arranged in front of the flashing part, there have been defects that it will be necessary to provide a liquid crystal member and liquid crystal controlling apparatus having nothing to do directly with the strobe apparatus and, as the light distribution characteristics are varied by shielding the effective rays with the liquid crystal or the like, the loss by the diffusion and heat generation will be so large that, even if the desired light distribution characteristics are obtained, the light amount radiated from the strobe apparatus will be greatly reduced.
In the case of the actual use, with the means disclosed in the publication of the above mentioned Japanese patent application publication No. 10921/1986, as, prior to the main flash, in order to measure the reflected light, infrared rays are projected and then the liquid crystal is driven, the release time lag after the photographer pushes down the shutter button until the exposure is actually made will be so long that the shutter chance will be likely to be missed. Also, there has been a defect that, as it is made a main aim to reduce the strobe light to the object adjacent to the main object, it will be effective only to prevent the object mostly at the near distance from being over exposed.